There’s a proposed SpaceX Mars mission called “Red Dragon”. Elon Musk can fund a half dozen of these missions, at an estimated price of $400 million, with his current fortune at retail prices. Six times 1,000 kilograms of payload to Mars seems like a very tight mass budget to handle a retirement. Fortunately, the mass budget may rise as prices drop.

Even 240 flights to Mars is probably not enough to create a comfortable retirement destination. Not unreasonably, Musk has a plan to make settling Mars a profitable business.

SpaceX has demonstrated its Grasshopper vehicle, which has proven SpaceX’s mastery of vertical landing. And there are more hints of reusability, the Holy Grail that can get the cost of a rocket flight down from greater than $100 million to less than $10 million. At $100 per pound, a flight to orbit is competitive with a first-class flight to Australia. But where is there to go?